NodeMetaRef:{to,from}_table and lua_api.txt additions

src/map.cpp

@@ -1009,6 +1009,12 @@ void Map::addNodeAndUpdate(v3s16 p, MapNode n,
 		n.setLight(LIGHTBANK_DAY, LIGHT_SUN, nodemgr);
 	}
 
+	/*
+		Remove node metadata
+	*/
+
+	removeNodeMetadata(p);
+
 	/*
 		Set the node on the map
 	*/
@@ -3451,15 +3457,15 @@ MapBlock* ServerMap::loadBlock(v3s16 blockpos)
 		}
 		catch(InvalidFilenameException &e)
 		{
-			return false;
+			return NULL;
 		}
 		catch(FileNotGoodException &e)
 		{
-			return false;
+			return NULL;
 		}
 		catch(std::exception &e)
 		{
-			return false;
+			return NULL;
 		}
 	}